IDBIndex.openCursor()

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This article is in need of a technical review.

The openCursor() method of the IDBIndex interface returns an IDBRequest object, and, in a separate thread, creates a cursor over the specified key range.

The method sets the position of the cursor to the appropriate record, based on the specified direction.

  • If the key range is not specified or is null, then the range includes all the records.
  • A success event is always fired on the result object.
    • If at least one record matches the key range then the result property of the event is set to the new IDBCursor object; the value of the cursor object is set to a structured clone of the referenced value.
    • If no records match the key range then then the result property of the event is set to null.

Syntax

var myIndex = objectStore.index('index');
var request = myIndex.openCursor();

Returns

An IDBRequest object on which subsequent events related to this operation are fired.

Exceptions

This method may raise a DOMException with a DOMError of one of the following types:

Exception Description
TransactionInactiveError This IDBIndex's transaction is inactive.
TypeError The value for the direction parameter is invalid.
DataError

The key or key range provided contains an invalid key.

InvalidStateError The IDBIndex has been deleted or removed.

Example

In the following example we open a transaction and an object store, then get the index lName from a simple contacts database. We then open a basic cursor on the index using openCursor() — this works the same as opening a cursor directly on an ObjectStore using IDBObjectStore.openCursor except that the returned records are sorted based on the index, not the primary key.

Finally, we iterate through each record, and insert the data into an HTML table. For a complete working example, see our IDBIndex-example demo repo (View the example live.)

function displayDataByIndex() {
  tableEntry.innerHTML = '';
  var transaction = db.transaction(['contactsList'], 'readonly');
  var objectStore = transaction.objectStore('contactsList');

  var myIndex = objectStore.index('lName'); 

  myIndex.openCursor().onsuccess = function(event) {
    var cursor = event.target.result;
    if(cursor) {
      var tableRow = document.createElement('tr');
      tableRow.innerHTML =   '<td>' + cursor.value.id + '</td>'
                           + '<td>' + cursor.value.lName + '</td>'
                           + '<td>' + cursor.value.fName + '</td>'
                           + '<td>' + cursor.value.jTitle + '</td>'
                           + '<td>' + cursor.value.company + '</td>'
                           + '<td>' + cursor.value.eMail + '</td>'
                           + '<td>' + cursor.value.phone + '</td>'
                           + '<td>' + cursor.value.age + '</td>';
      tableEntry.appendChild(tableRow);  

      cursor.continue();
    } else {
      console.log('Entries all displayed.');    
    }
  };
};

Parameters

range
Optional. The key range to use as the cursor's range.
direction
Optional. The cursor's direction. See IDBCursor Constants for possible values.

Specification

Specification Status Comment
Indexed Database API
The definition of 'openCursor()' in that specification.
Candidate Recommendation  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 23webkit
24
10 moz
16.0 (16.0)
10, partial 15 7.1
count() 23 22.0 (22.0) 10, partial 15 7.1
getAll() and getAllKeys() Not supported 24.0 (24.0)
behind dom.indexedDB.experimental  pref
Not supported Not supported Not supported
Feature Android Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support 4.4 22.0 (22.0) 1.0.1 10 22 Not supported
count() 4.4 22.0 (22.0) 1.0.1 10 22 Not supported
getAll() and getAllKeys() Not supported 24.0 (24.0)
behind dom.indexedDB.experimental  pref
1.1 behind
dom.indexedDB.experimental  pref
Not supported Not supported Not supported

Be careful in Chrome as it still implements the old specification along the new one. Similarly it still has the prefixed webkitIndexedDB property even if the unprefixed indexedDB is present.

See also

Document Tags and Contributors

Contributors to this page: fscholz, chrisdavidmills, Bent
Last updated by: fscholz,